Melanoma Skin Cancer Stages

After someone is diagnosed with melanoma, doctors will try to figure out if it has spread, and if so, how far. This process is called staging. The stage of a cancer describes how much cancer is in the body. It helps determine how serious the cancer is and how best to treat it. Doctors also use a cancer’s stage when talking about survival statistics.

Although each person’s cancer experience is unique, cancers with similar stages tend to have a similar outlook and are often treated in much the same way.

How is the stage determined?

The staging system most often used for melanoma is the American Joint Committee on Cancer (AJCC) TNM system, which is based on 3 key pieces of information:

The main (primary) tumor (T): How deep has the cancer grown into the skin? Is the cancer ulcerated?

• Tumor thickness: The thickness of the melanoma is called the Breslow measurement. In general, melanomas less than 1 millimeter (mm) thick (about 1/25 of an inch) have a very small chance of spreading. As the melanoma becomes thicker, it has a greater chance of spreading.
• Ulceration: Ulceration is a breakdown of the skin over the melanoma. Melanomas that are ulcerated tend to have a worse outlook.

Spread to nearby lymph nodes (N): Has the cancer reached nearby lymph nodes?

Spread (metastasis) to distant parts of the body (M): Has the cancer spread to distant lymph nodes, skin, or other organs? (Melanoma can spread almost anywhere in the body, but the most common sites of spread are the lungs, liver, brain, bones, and the skin or lymph nodes in other parts of the body.)

Numbers or letters after T, N, and M provide more details about each of these factors. Higher numbers mean the cancer is more advanced.

Once a person’s T, N, and M categories have been determined, this information is combined in a process called stage grouping to assign an overall stage.

The earliest stage melanomas are stage 0 (melanoma in situ), and then range from stages I (1) through IV (4). Some stages are split further, using capital letters (A, B, etc.). As a rule, the lower the number, the less the cancer has spread. A higher number, such as stage IV, means cancer has spread more. And within a stage, an earlier letter means a lower stage.

There are 2 main types of staging for melanoma.

• The clinical stage is based on the results of physical exams, biopsies, and any imaging tests that have been done (as described in Tests for Melanoma Skin Cancer).
• After the skin biopsy to confirm the diagnosis, if surgery is done (to remove more of the area around the skin tumor, as well as to check nearby lymph nodes for cancer), the pathological stage (also called the surgical stage) can be determined.

The clinical stage can be used to help determine if more tests need to be done, to help plan treatment, and to give an idea of a person’s outlook. Sometimes, though, the cancer might have spread farther than the clinical stage estimates, so it may not predict a person’s outlook as accurately as a pathological stage.

To learn more about how cancer is staged, see Cancer Staging.

Stages of melanoma

The table below is a simplified version of the clinical stages in the most recent TNM system, effective as of 2018. If your cancer has been pathologically staged, it is best to talk to your doctor about your specific stage.

Melanoma staging can be very complex, so if you have any questions about the stage of your cancer or what it means, ask your doctor to explain it to you in a way you understand.

AJCC Clinical  Stage	Stage Description
0	The cancer is confined to the epidermis, the outermost skin layer (Tis). There are no signs the cancer has spread to nearby lymph nodes (N0) or to distant parts of the body (M0). This stage is also known as melanoma in situ.
I	The main tumor is no more than 2 mm (about 2/25 of an inch) thick and might or might not be ulcerated (T1 or T2a). There are no signs the cancer has spread to nearby lymph nodes (N0) or to distant parts of the body (M0). (Stage I is further divided into stages IA and IB, based on tumor thickness and if it’s ulcerated.)
II	The main tumor is more than 1 mm thick (T2b or T3) and may be thicker than 4 mm (T4). It might or might not be ulcerated. There are no signs the cancer has spread to nearby lymph nodes (N0) or to distant parts of the body (M0). (Stage II is further divided into stages IIA, IIB, and IIC, based on tumor thickness and if it’s ulcerated.)
III	The main tumor can be any thickness, and it might or might not be ulcerated (any T). The cancer has spread to nearby lymph nodes and/or it has spread to very small areas of nearby skin (satellite tumors) or to skin lymphatic channels around the tumor (N1, N2, or N3). There are no signs the cancer has spread to distant parts of the body (M0).
IV	The main tumor can be any thickness, and it might or might not be ulcerated (any T). The cancer might or might not have spread to nearby lymph nodes (any N). The cancer has spread to distant parts of the body, such as: Areas of skin or lymph nodes in other parts of the body (M1a) The lung(s) (M1b) Any other organs outside the central nervous system (M1c) The central nervous system, including the brain, spinal cord, and the coverings of the brain and spinal cord (M1d)